Standardize positional datamodule and argument names

CHANGELOG.md

@@ -29,6 +29,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
     [#7574](https://github.com/PyTorchLightning/pytorch-lightning/pull/7574))
 
 
+- Added support for passing a `LightningDataModule` positionally as the second argument to `trainer.{validate,test,predict}` ([#7431](https://github.com/PyTorchLightning/pytorch-lightning/pull/7431))
+
+
 - Added argument `trainer.predict(ckpt_path)` ([#7430](https://github.com/PyTorchLightning/pytorch-lightning/pull/7430))
 
 
@@ -160,6 +163,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 ### Deprecated
 
 
+- Standardized the dataloaders arguments of `trainer.{fit,valdiate,test,tune}` ([#7431](https://github.com/PyTorchLightning/pytorch-lightning/pull/7431))
+
+
 - Deprecated `DataModule` properties: `has_prepared_data`, `has_setup_fit`, `has_setup_validate`, `has_setup_test`, `has_setup_predict`, `has_teardown_fit`, `has_teardown_validate`, `has_teardown_test`, `has_teardown_predict` ([#7657](https://github.com/PyTorchLightning/pytorch-lightning/pull/7657/))
 
 

docs/source/advanced/multiple_loaders.rst

@@ -91,23 +91,6 @@ For more details please have a look at :paramref:`~pytorch_lightning.trainer.tra
 Furthermore, Lightning also supports that nested lists and dicts (or a combination) can
 be returned.
 
-.. testcode::
-
-    class LitModel(LightningModule):
-
-        def train_dataloader(self):
-
-            loader_a = torch.utils.data.DataLoader(range(8), batch_size=4)
-            loader_b = torch.utils.data.DataLoader(range(16), batch_size=2)
-
-            return {'a': loader_a, 'b': loader_b}
-
-        def training_step(self, batch, batch_idx):
-            # access a dictionnary with a batch from each dataloader
-            batch_a = batch["a"]
-            batch_b = batch["b"]
-
-
 .. testcode::
 
     class LitModel(LightningModule):

docs/source/common/lightning_module.rst

@@ -441,12 +441,12 @@ There are two ways to call `test()`:
     trainer.fit(model)
 
     # automatically auto-loads the best weights
-    trainer.test(test_dataloaders=test_dataloader)
+    trainer.test(dataloaders=test_dataloader)
 
     # or call with pretrained model
     model = MyLightningModule.load_from_checkpoint(PATH)
     trainer = Trainer()
-    trainer.test(model, test_dataloaders=test_dataloader)
+    trainer.test(model, dataloaders=test_dataloader)
 
 ----------
 

docs/source/common/test_set.rst

@@ -80,10 +80,10 @@ is not available at the time your model was declared.
 .. code-block:: python
 
     # setup your data loader
-    test = DataLoader(...)
+    test_dataloader = DataLoader(...)
 
     # test (pass in the loader)
-    trainer.test(test_dataloaders=test)
+    trainer.test(dataloaders=test_dataloader)
 
 You can either pass in a single dataloader or a list of them. This optional named
 parameter can be used in conjunction with any of the above use cases. Additionally,

docs/source/common/trainer.rst

@@ -159,7 +159,7 @@ or after it has already been trained.
 
 .. code-block:: python
 
-    trainer.validate(val_dataloaders=val_dataloaders)
+    trainer.validate(dataloaders=val_dataloaders)
 
 ------------
 

docs/source/extensions/datamodules.rst

@@ -53,7 +53,7 @@ Datamodules are for you if you ever asked the questions:
 
 What is a DataModule
 --------------------
-A DataModule is simply a collection of a train_dataloader, val_dataloader(s), test_dataloader(s) along with the
+A DataModule is simply a collection of a train_dataloader(s), val_dataloader(s), test_dataloader(s) along with the
 matching transforms and data processing/downloads steps required.
 
 Here's a simple PyTorch example:

pytorch_lightning/core/hooks.py

@@ -13,14 +13,13 @@
 # limitations under the License.
 """Various hooks to be used in the Lightning code."""
 
-from typing import Any, Dict, List, Optional, Union
+from typing import Any, Dict, List, Optional
 
 import torch
 from torch.optim.optimizer import Optimizer
-from torch.utils.data import DataLoader
 
 from pytorch_lightning.utilities import move_data_to_device, rank_zero_warn
-from pytorch_lightning.utilities.types import STEP_OUTPUT
+from pytorch_lightning.utilities.types import EVAL_DATALOADERS, STEP_OUTPUT, TRAIN_DATALOADERS
 
 
 class ModelHooks:
@@ -428,14 +427,13 @@ def teardown(self, stage: Optional[str] = None) -> None:
             stage: either ``'fit'``, ``'validate'``, ``'test'``, or ``'predict'``
         """
 
-    def train_dataloader(self) -> Union[DataLoader, List[DataLoader], Dict[str, DataLoader]]:
+    def train_dataloader(self) -> TRAIN_DATALOADERS:
         """
         Implement one or more PyTorch DataLoaders for training.
 
         Return:
-            Either a single PyTorch :class:`~torch.utils.data.DataLoader` or a collection of these
-            (list, dict, nested lists and dicts). In the case of multiple dataloaders, please see
-            this :ref:`page <multiple-training-dataloaders>`
+            A collection of :class:`torch.utils.data.DataLoader` specifying training samples.
+            In the case of multiple dataloaders, please see this :ref:`page <multiple-training-dataloaders>`.
 
         The dataloader you return will not be called every epoch unless you set
         :paramref:`~pytorch_lightning.trainer.Trainer.reload_dataloaders_every_epoch` to ``True``.
@@ -503,7 +501,7 @@ def train_dataloader(self):
         """
         rank_zero_warn("`train_dataloader` must be implemented to be used with the Lightning Trainer")
 
-    def test_dataloader(self) -> Union[DataLoader, List[DataLoader]]:
+    def test_dataloader(self) -> EVAL_DATALOADERS:
         r"""
         Implement one or multiple PyTorch DataLoaders for testing.
 
@@ -533,7 +531,7 @@ def test_dataloader(self) -> Union[DataLoader, List[DataLoader]]:
             There is no need to set it yourself.
 
         Return:
-            Single or multiple PyTorch DataLoaders.
+            A :class:`torch.utils.data.DataLoader` or a sequence of them specifying testing samples.
 
         Example::
 
@@ -563,7 +561,7 @@ def test_dataloader(self):
             will have an argument ``dataloader_idx`` which matches the order here.
         """
 
-    def val_dataloader(self) -> Union[DataLoader, List[DataLoader]]:
+    def val_dataloader(self) -> EVAL_DATALOADERS:
         r"""
         Implement one or multiple PyTorch DataLoaders for validation.
 
@@ -584,7 +582,7 @@ def val_dataloader(self) -> Union[DataLoader, List[DataLoader]]:
             There is no need to set it yourself.
 
         Return:
-            Single or multiple PyTorch DataLoaders.
+            A :class:`torch.utils.data.DataLoader` or a sequence of them specifying validation samples.
 
         Examples::
 
@@ -614,7 +612,7 @@ def val_dataloader(self):
             will have an argument ``dataloader_idx`` which matches the order here.
         """
 
-    def predict_dataloader(self) -> Union[DataLoader, List[DataLoader]]:
+    def predict_dataloader(self) -> EVAL_DATALOADERS:
         r"""
         Implement one or multiple PyTorch DataLoaders for prediction.
 
@@ -632,7 +630,7 @@ def predict_dataloader(self) -> Union[DataLoader, List[DataLoader]]:
             There is no need to set it yourself.
 
         Return:
-            Single or multiple PyTorch DataLoaders.
+            A :class:`torch.utils.data.DataLoader` or a sequence of them specifying prediction samples.
 
         Note:
             In the case where you return multiple prediction dataloaders, the :meth:`predict`

pytorch_lightning/trainer/connectors/data_connector.py

@@ -12,17 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import List, Optional, Union
-
-from torch.utils.data import DataLoader
+from typing import Optional, Union
 
 import pytorch_lightning as pl
 from pytorch_lightning.trainer.supporters import prefetch_iterator
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from pytorch_lightning.utilities.model_helpers import is_overridden
+from pytorch_lightning.utilities.types import EVAL_DATALOADERS, TRAIN_DATALOADERS
 
 
-class DataConnector(object):
+class DataConnector:
 
     def __init__(self, trainer: "pl.Trainer", multiple_trainloader_mode: str = "max_size_cycle"):
         self.trainer = trainer
@@ -71,16 +70,16 @@ def can_prepare_data(self):
     def attach_data(
         self,
         model: 'pl.LightningModule',
-        train_dataloader: Optional[Union[DataLoader, List[DataLoader]]] = None,
-        val_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
-        test_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
-        predict_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
+        train_dataloaders: Optional[TRAIN_DATALOADERS] = None,
+        val_dataloaders: Optional[EVAL_DATALOADERS] = None,
+        test_dataloaders: Optional[EVAL_DATALOADERS] = None,
+        predict_dataloaders: Optional[EVAL_DATALOADERS] = None,
         datamodule: Optional['pl.LightningDataModule'] = None
     ) -> None:
         # set up the passed in dataloaders (if needed)
         self.attach_dataloaders(
             model,
-            train_dataloader=train_dataloader,
+            train_dataloaders=train_dataloaders,
             val_dataloaders=val_dataloaders,
             test_dataloaders=test_dataloaders,
             predict_dataloaders=predict_dataloaders,
@@ -92,15 +91,15 @@ def attach_data(
     def attach_dataloaders(
         self,
         model: 'pl.LightningModule',
-        train_dataloader: Optional[Union[DataLoader, List[DataLoader]]] = None,
-        val_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
-        test_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
-        predict_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
+        train_dataloaders: Optional[TRAIN_DATALOADERS] = None,
+        val_dataloaders: Optional[EVAL_DATALOADERS] = None,
+        test_dataloaders: Optional[EVAL_DATALOADERS] = None,
+        predict_dataloaders: Optional[EVAL_DATALOADERS] = None,
     ) -> None:
         # when dataloader is passed via fit, patch the train_dataloader
         # functions to overwrite with these implementations
-        if train_dataloader is not None:
-            model.train_dataloader = _PatchDataLoader(train_dataloader)
+        if train_dataloaders is not None:
+            model.train_dataloader = _PatchDataLoader(train_dataloaders)
 
         if val_dataloaders is not None:
             model.val_dataloader = _PatchDataLoader(val_dataloaders)
@@ -140,23 +139,22 @@ def attach_datamodule(
                 model.data_pipeline = datamodule.data_pipeline
 
 
-class _PatchDataLoader(object):
+class _PatchDataLoader:
     r"""
     Callable object for patching dataloaders passed into trainer.fit().
     Use this class to override model.*_dataloader() and be pickle-compatible.
 
     Args:
         dataloader: Dataloader object to return when called.
-
     """
 
-    def __init__(self, dataloader: Union[List[DataLoader], DataLoader]):
+    def __init__(self, dataloader: Union[TRAIN_DATALOADERS, EVAL_DATALOADERS]) -> None:
         self.dataloader = dataloader
 
         # cannot pickle __code__ so cannot verify if PatchDataloader
         # exists which shows dataloader methods have been overwritten.
         # so, we hack it by using the string representation
         self.patch_loader_code = str(self.__call__.__code__)
 
-    def __call__(self) -> Union[List[DataLoader], DataLoader]:
+    def __call__(self) -> Union[TRAIN_DATALOADERS, EVAL_DATALOADERS]:
         return self.dataloader